Blast furnace tuyere

ABSTRACT

A blast furnace tuyere has a nozzle with a double tubular jacket wall between which there flows a cooling fluid which is guided by a flow guide installed between the two jacket walls, so that the cooling fluid flows over the inner surfaces of the two jacket walls around the guide. The flow guide occupies substantially the whole of the space between the inner and outer jacket walls adjacent to the nozzle mouth, leaving only a narrow gap through which the cooling fluid can flow.

United States Patent Preisendanz et al.

' 1 1 Sept. 26, 1972 FOREIGN PATENTS OR APPLICATIONS [54] BLAST FURNACE TUYERE 1 2] Inventors: Hans Preisendnnz, Moltkestrasse 174,930 5/1953 Austria ..266/41 Willich; Georg Schnegelsberg, Saarner Strasse 497, Mulheim-Speldarf; Peter Schuler, Cracauerstr. 75, Primary Baldwin Krefeld; Hans Krause, Jordinstrasse y and Tore" 2, Duisburg-Ruhrort, all of Germany [57] ABSTRACT [22] Filed: Nov. 4, 1970 A blast furnace tuyere has a nozzle with a double tulzl] Appl' 86,648 bular jacket wall between which there flows a cooling fluid which is guided by a flow guide installed between [30] Foreign Application Priority Data the two jacket walls, so that the cooling fluid flows Nov. 5 1969 Germany 19 5476 over the inner surfaces of the two jacket walls around July 25, 1970 Germany "P 20 37 011.0 the guide. The flow guide occupies substantially the Y t whole of the space between the inner and outer jacket 52 us. (:1. ..266/41, /1825, 122/6.6 walls adjacent to the nozzle mouth, leaving y a 51 Int. Cl. ..C2lb 7/16 row p through which h cooling fluid can [58] Field of Search ..266/41; 122/6.6; /147;

[56] References Cited 21 Claims, 12 Drawing Figures UNITED STATES PATENTS 2,145,650 1/1939 Fox ..122/6.6

i 23 n 1' 21 3 7 1Q.

PATENTED EP I912 3.693.961

SHEEI 3 OF 6 INVENTORS HANS PR6! END NZ EORG SCH EGEL BERG BY TER SCHULER HANS HRAUSE ?&apa 7p Em2 077C ATTORNEYfi PATENTEBsms m2 SHEET 6 BF 6 FIG. 11

m dw

EELS

NBN MR IEWWM 0 H m m m BLAST FURNACE TUYERE The invention relates to a blast furnace tuyere with a nozzle which projects into the interior of the blast furnace, the nozzle having a double tubular jacket wall consisting of an inner jacket wall and an outer jacket wall, between which there flows a cooling fluid, which is guided by a flow guide installed between the two jacket walls, so that the cooling fluid flows over the inner surfaces of the two jacket walls around the guide.

Blast furnace tuyeres of this kind are subjected in operation to a very high heat flux. Consequently if the tuyere is to have a reasonably long working life all its parts must be adequately cooled.

It is important to ensure that the cooling fluid acts effectively on the entire interior wall surface of the double jacket. A variety of solutions have been proposed to solve this problem.

. In one proposed solution the flow guide has an outlet slot for cooling water, directed towards the tuyere nozzle mouth. From this slot water is ejected to impinge against the inner surface of the double jacket wall, the water then flowing back equally over the surfaces of the inner and outer jacket walls, finally issuing from the base of the tuyere nozzle and flowing away through an effluent pipe. However this arrangement does not ensure a sufficient flow of cooling water over the inner surface of the outer jacket wall, which is subjected to the highest heat flux. The distribution of flow velocity, and mass rate of flow of water, between the surfaces of the inner and outer jacket walls depends on the flow resistances,which are by no means constant.

I Compared to this solution an improvement has been proposed in the German Pat. No. 719,138. According to this proposalthe cooling water is introduced at the base of the tuyere nozzle and flows through the space between the jacket walls guided by a flow guide, which guides the water so that it flows forwards, towards the nozzle mouth, over the inner surface of the outer jacket wall, returning over the surface of the inner jacket wall. Near the tuyere nozzle mouth the stream of water is deflected through 180. However in this known proposal the channel along which the water flows increases in cross section in the region of the 180 bend, with the result that the linear velocity of flow decreases. The purpose of this is to ensure that the water makes adequate contact with the entire jacket wall surface near the nozzle mouth, where the highest heat flux occurs.

- This kind of tuyere has not proved satisfactory in practice, because vapor bubbles form on the inner surface of the jacket wall at the bend in the flow path, where the water is deflected through 180. The vapor I bubbles impede heat transfer just in the region where the heat flux is greatest. The inner surface of the jacket wall can suffer damage from overheating, and in the extreme case the jacket wall can be rapidly destroyed.

The object of the present invention is to provide a blast furnace tuyere of the kind mentioned at the beginning, capable of withstanding the high heat loads which occur in the interior of a blast furnace. The problem is solved by. the invention essentially in that in the region of the nozzle mouth the flow guide occupies substantially the whole of the space between the inner and outer jacket walls, leaving only a comparatively narrow gap through which the cooling fluid flows along the jacket wall surfaces. Instead of the flow channel becoming wider towards the nozzle mouth, it becomes narrower, the remaining gap being specially constructed to provide a linear acceleration of the cooling fluid in the region of the nozzle mouth.

The width of the gap is preferably less than 5 mm, at least where the cooling fluid flows over the surface of the outer jacket wall. Using water as the cooling fluid, the linear velocity of flow through the gap is higher than 8 m/sec, and is preferably 15 'm/sec. The gap has as nearly as possible a constant cross sectional area, so that the water flows in the gap at a constant linear velocity, in the region of the nozzle mouth.

In accordance with a further feature of the invention, the vapor bubbles are not only almost immediately torn off the inner surface of the jacket wall, but are inhibited in their formation by the fact that a positive pressure higher than 0.5 atmospheres gauge is maintained at the cooling fluid outlet opening, so that the cooling fluid is under at least this amount of pressure all the way along its path. The pressure at the outlet is preferably between 1 and 2 atmospheres gauge. This pressure inhibits detachment of the cooling fluid from the inner surfaces of the double jacket walls.

When a cooling fluid is flowing over a wall surface it tends to become detached from the surface at sharp edges, rough places and the like. In regard to heat transfer this effect is equivalent to the formation of vapor bubbles. According to the invention detachment is prevented in that the gap through which the cooling fluid flows follows a path, as seen in longitudinal section, which curves over, following approximately an arc of a circle, in the region where the flow path is deflected, that is to say near the nozzle mouth. The flow path is therefore free from sudden changes in direction and sharp edges.

The wall of the flow guide preferably increases in thickness towards the nozzle mouth, forming a narrow gap between the flow guide and the jacket wall. To retain the flow guide accurately in position, so that the gap width remains constant, longitudinal spacer ribs are introduced, that is to say longitudinal with respect to the longitudinal middle axis of the nozzle. The ribs support the flow guide at the specified distance from the jacket wall, ensuring that the gap retains the desired shape. The ribs also help to stiffen the structure. A large number of ribs can be used, preferably equally spaced apart, which divide the gap into a number of longitudinal flow channels. The resulting channels are calculated so that the cooling fluid acts approximately equally over the entire inner surface of the double walled jacket in the region of the nozzle mouth.

The even distribution of flow of the cooling fluid is further promoted in that the cooling fluid is admitted to the nozzle through a number of inlet openings distributed equally around in a circle, the coolingv fluid leaving the nozzle through a number of outlet openings, also equally distributed around in a circle. The cooling fluid is fed to the inlet openings through a common annular feed chamber supplied with fluid through an inlet pipe. Similarly the cooling fluid is discharged through the outlet openings into a common annular chamber from where the fluid flows away through an effluent pipe.

The ribs are preferably made projecting from the jacket'wall. Each rib has a width which is less than the width of the flow gap. The channels are preferably of the same width as the ribs. This gives the channels cross sections which discourage foreign bodies from becoming lodged, choking up the channels, in the case where water is used as the cooling fluid. Furthermore this shape of rib gives the best heat transfer from the double walled jacket to the cooling fluid.

To simplify heat transfer and manufacture, the wall thickness of the double jacket is constant in the region of the gap. The wall thickness is considerably less than the radius of curvature of the gap, as seen in longitudinal section.

Manufacture is simplified by constructing the double walled jacket in several parts. This allows the nozzle to be assembled by assembling the double walled jacket around the flow guide.

The nozzle can be an assembly of several axial parts. In this case the nozzle consists of at least two parts, a nozzle neck and a replaceable nozzle head. This arrangement not only simplifies manufacture but has the particular advantage that if the nozzle head becomes damaged the nozzle neck still remains operative. The cooling of the nozzle head is preferably independent of the cooling of the nozzle neck, so that if the nozzle head becomes damaged the tuyere can still continue in operation, after the cooling of the nozzle head has been interrupted. In tuyeres of the customary kind as soon as a nozzle head becomes damaged the entire blast furnace has to be shut down immediately.

If the nozzle is U-shaped in cross section, the nozzle or the flow guide can be manufactured in a simple way but with great precision bydeep drawing. The flow guide according to the invention can be made of a flexible and/or highly elastic and/or a plastic material of construction. In this case even if the nozzle is complex or highly curved in cross section the flow guide can be introduced into the nozzle and subsequently inflated to its final shape by hydraulic or pneumatic inflation. The flow guide is preferably made of rubber or a similar material, or it can be made of glass fiber reinforced plastic, or of copper. The pressure fluid for the inflation can for example be a liquid or pasty hardening substance, whichis injected into the interior of the hollow flow guide, where it remains after hardening. The hardening substance'can for example be a hardening plastic or a concrete. The resulting flow guide, which is initially comparatively flexible, is given a high degree of rigidity by this method. Alternatively the flow guide can initially be a comparatively stiff structure. In this case the flow guide is inflated by introducing a liquid or a gas under pressure. After inflation and removal of the pressure fluid, the inflated flow guide retains its shape.

The presence of the ribs facilitates this method of manufacture, in that the flow guide can simply be inflated until its outer surface rests everywhere in contact with the edges of the ribs.

Several examples of tuyeres in accordance with the invention are represented in the accompanying drawings, in which:

FIG. 1 shows, in longitudinal section, a tuyere according to the invention through which hot air is blown into the hearth of a blast furnace;

FIG. 2 shows, on the right of the line Z Z, a cross section taken along the line II II in FIG. 1, and on the left of the line Z Z a corresponding cross section through a modification;

FIG. 3 is a cross section taken along the line III III in FIG. 1;

FIG. 4 is a longitudinal section through a third examle; p FIG. 5 is an end view corresponding to FIG. 4;

FIG. 6 is a cross section taken along the line VI VI in FIG. 4;

FIG. 7 is a section taken along the line VII VII in FIG. 5;

FIG. 8 is a longitudinal section through a fourth example of a tuyere, showing on the left of the line Z Z the tuyere during assembly, and on the right of the line Z Z the tuyere ready for operation;

FIG. 9 is a cross section taken along the line IX IX in FIG. 8;

FIG. 10 is a cross section taken along the line X X in FIG. 8;

FIG. 11 is a longitudinal section through a fifth tuyere, showing on the left of the line Z Z the tuyere during assembly, and on the right of the line Z Z the tuyere ready for operation; and,

FIG. 12 is a cross section taken along the line XII XII in FIG. 11.

The tuyere according to the invention is mounted in the side of a blast furnace (not shown) with its nozzle 7 projecting inwards into the interior of the blast furnace, The nozzle 7 is in the form of a truncated cone and has a double walled jacket 4, with an inner wall and an outer wall. At the nozzle mouth the inner wall curves outwards seamlessly in a curve of constant radius to form the outer wall, so that in cross section the double wall 4 is of hairpin shape. The thickness of the double wall 4 is constant and considerably less than the radius of curvature at the transition between the inner wall and the outer wall. The double wall 4 is made of a highly heat conductive material, preferably copper. If desired the double wall 4 can have an outer coating in the form of a layer of refractory material, for example graphite or a ceramic or the like.

At its base the double walled jacket 4 is sealed to a barrel 1 by an outer weld seam 5 which joins the outer jacket to the barrel, and an inner weld seam 6 which joins the inner wall to the barrel 1.

Near its base the double walled jacket 4 contains a bulkhead wall 8 in a transverse plane, that is to say in a plane perpendicular to the longitudinal axis of the double walled jacket. The bulkhead wall 8 is situated at a distance forward of the barrel 1, this distance being less than the widest gap between the inner and outer walls of the double walled jacket 4, but more than half this gap. The bulkhead wall 8 divides the interior of the double walled jacket into two chambers, the chamber nearest to the barrel 1 being limited by the barrel 1, the bulkhead wall 8 and the inner and outer walls of the double walled jacket 4. This chamber is itself subdivided, as shown in FIG. 3, by an annular wall 9, which extends parallel to the inner end and outer walls of the double walled jacket 4, into two annular chambers, an outer annular chamber 10 and an inner annular chamber 11, the annular wall 9 forming a good seal between these two annular chambers.

The outer annular chamber has an opening 2 in the nose of the barrel 1, and similarly the inner annular chamber 11 has an opening 3 in the nose of the barrel 1. The diameter of the opening 3 is greater than the gap between the intermediate annular wall 9 and the inner wall of the double walled jacket 4. To give room for this opening the outer annular chamber 10 is blanked off on either side of the opening 3, by two welded walls 13 extending approximately radially between the intermediate annular wall 9 and the outer jacket wall. Similarly and for the same reason the inner annular chamber 11 is blanked ofi by radial welded walls on either side of the opening 2. The intermediate annular wall 9 is interrupted at these two locations, giving clear openings 14 and 15 large enough to give clear room for the openings 2 and 3.

If desired the openings 2 and 3 can be positioned non-diametrical, as shown in FIG. 3, the barrel 1 being circular. In this case FIG. 1 is a longitudinal section taken through the tuyere along the line I I in FIG. 3.

The outer annular chamber 10 has, in the bulkhead wall 8, a number of equally spaced openings 16 located on a circle, and similarly the inner annular chamber 11 has equally spaced openings 17. When the tuyere is in operation a cooling fluid flows from the barrel 1 through the opening 2, through the outer annular chamber 10 and through the openings 16 into the hollow space between the walls of the double walled jacket 4, returning through the openings 17, the inner annular chamber 1 l and the openings 3 back into the barrel 1.

The cooling fluid entering the hollow space between the walls of the jacket is deflected and guided by a flow guide 20, which guides the fluid so that it flows forwards to the mouth of the nozzle before returning to the base. I

The flow guide 20 can if desired by made of the same material or construction as the double walled jacket 4, or alternatively if desired it can be made of some other, rust resistant material such as stainless steel or the like. The flow guide 20 is an annular body somewhat wedge shaped in longitudinal section. A longitudinal section through the flow guide 20 shows that its wall varies in thickness the wall becoming thinner towards the base 20a of the flow guide, where the wall thickness is only enough to support mechanical stresses. At its base the flow guide 20 is welded to the bulkhead wall 8. The nose end 20b, or nozzle mouth end of the flow guide has a greater wall thickness, the flow guide occupying most of the space between the jacket walls in this region, that is to say in the region of the nozzle mouth, so that only a comparatively narrow gap remains in this region between the flow guide and the jacket walls. The remaining annular gap 21 is hairpin shaped in longitudinal section. Its width is little compared to the radius of curvature of the hairpin bend. However the gap 21, as seen in longitudinal section, increases towards the interior of the nozzle, that is to say increases from the outer jacket wall towards the inner jacket wall, so that the total cross sectional area across which the coolant fluid flows remains constant along the path of flow of the fluid. Where the fluid flows in contact with the outer jacket wall, near the tuyere nozzle mouth, the width of the gap 21 is less than 5 mm, preferably less than 2 mm.

' ticular to maintain its width near the nozzle mouth, that is to say to maintain the distance between the thicker part 20b of the flow guide and the jacket wall surfaces, the outer jacket wall, near the nozzle month, has three narrow longitudinal spacer ribs 22 spaced apart,

as shown in FIG. 2 to the left of the line Z Z. The

spacer ribs also help to stiffen the structure.

Alternatively there can be a large number of spacer ribs 22, providing still greater rigidity to the structure. A large number of spacer ribs has the further advantage that a greater contact area is available for the coolant fluid, for cooling the inner surface of the double walled jacket 4. In order to obtain the highest possible rate of heat transfer a large number of spacer ribs is used, the number being calculated by the method of E. Schmidt. FIG. 2, t0 the right of the line Z Z, shows spacer ribs 23, to give the highest heat transfer rate. In this case the gap 21, between the thick part 20b of the flow guide 20 and the outer jacket wall consists of a number of individual, longitudinal flow channels 24 which between them provide the same flow cross sectional area as is provided by the 3 channels represented to the left of the Z Z line in FIG. 2. The large number of channels shown to the right of the Z Z line gives the further advantage that each channel can be deeper, that is to say if numerous channels are used the distance between the thicker part 20b of the flow guide 20 and the inner surface of the jacket wall can be greater, for the same total flow cross sectional area, and consequently there is less risk of the channels becoming choked by foreign bodies, assuming that water is used as the cooling fluid.

As already mentioned, the flow cross sectional area remains constant over the length of the path of flow, outwards towards the nozzle mouth and back again towards the nozzle base. To obtain this the ribs 23 themselves become narrower towards the interior of the tuyere, that is to say they are narrower where they project outwards from the inner jacket wall, as shown clearly in FIG. 2.

To facilitate assembly of the tuyere nozzle, the double walled jacket 4 is made in two parts, a base part 40 and a nozzle mouth part 41;. The latter contains the ribs 23. As shown at 25 in FIG. 1 the ribs 23 where they project from the inner jacket wall have edges 25 extending exactly parallel to the nozzle longitudinal axis. During assembly of the tuyere the annular flow guide 26 is pushed into the nozzle mouth part of the jacket, the inner surface of the thicker part 20b of the -flow guide sliding along the parallel edges 25 of the ribs 23, whereupon the nozzle mouth jacket part 4b is welded at 26 to the nozzle base part 4a.

When the tuyere is in operation hot air is blown through it, the nozzle 7 being surrounded by molten iron and glowing coke and therefore subjected to a high heat flux. To keep the nozzle tolerably cool a cooling fluid, in particular water, is introduced through the opening 2, the water flowing through the outer annular chamber 10 and through the openings 16 into the annular space between the outer and inner double walled jacket 4. The cooling water is fed to the inlet opening 2 through a feed pipe which is not shown in the drawing. The cooling fluid, flowing through the outer openings 16 flows over the outer surface of the flow guide 20, out to the nozzle mouth, where it flows through the annular slot 21, or through the channels 24, returning over the inner surface of the flow guide 20 and finally leaving the nozzle through the openings 17 and chamber 11 and the opening 3. The water leaves the system through an effluent pipe which is not shown in the drawing. During its passage out and back through the double walled jacket 4 the water flows over the surfaces of the outer and inner walls of the double walled jacket 4, picking up a great deal of heat. The rate of heat transfer through the jacket wall is very high. If the flow of heat is impeded, for example by the formation of bubbles on the water surface of the jacket wall, the metal surface can become damaged and in the extreme case the tuyere nozzle 7 can be destroyed.

For safety of the tuyere it is necessary to ensure that the cooling fluid acts evenly over the entire surface of the double walled jacket 4. This is obtained in the present examples, in the first place by the even distribution of the openings 16 and 17, but in particular by the action of the channels 24, through which the fluid flows very evenly. The even flow is promoted, in the present example, in particular by the even curvature of the jacket wall at the nozzle mouth, that is to say between the outer and inner jacket walls. The cooling fluid has a smooth flow path all the way through the double walled jacket channels.

A further measure, to ensure an even cooling fluid action over the entire surface of the double walled jacket 4 is that the cooling fluid is conveyed under a considerable positive pressure, for example between 1 and 2 atmospheres gauge pressure, all the way through the flow channels. The water outlet pipe, which is not shown in the drawing contains water at this pressure, that is to say between 1 and 2 atmospheres gauge pressure, and consequently there is at least this much pressure all the way through the system, in particular in the interior of the double walled jacket 4. This positive water pressure reduces the risk of the cooling fluid becoming detached from the jacket wall surface, for example by sharp edges. Detachment of the fluid from the hot wall can result by the Leiden frost effect, by which vapor bubbles form on the hot surface, impeding heat transfer locally.

In the examples vapor bubbles forming on the inner surfaces of the double walled jacket 4 are torn off by the cooling fluid, which is travelling at high velocity. Even heat transfer over the entire transfer surface is therefore ensured. Using water as the cooling fluid linear flow velocities of 10 m/sec are therefore used in the gap 21 or in the channels 24. In the outer annular chamber 18 and in the inner annular chamber 19 the flow velocity is of course much lower, because the flow cross sectional area is greater, resistance to flow being correspondingly less.

FIG. 4 shows a further example of the tuyere according to the invention. In this example the nozzle consists of a nozzle head and a nozzle base 31. The nozzle base 31 is an assembly consisting of a barrel 32 and a nozzle neck 33. The nozzle neck 33 and the nozzle .8 head 30 both project inwards into the blast furnace. In this example, in contrast to the examples of FIGS. 1 to 3, the nozzle head 30 is detachable and exchangeable.

The flow guide 34 is contained entirely in the nozzle head 30.

In analogy to the examples of FIGS. 1 and 3, the nozzle head 30 has annular chambers 10 and 11, a channel plate 35 and a bulkhead wall 36. The chamber between is subdivided by an annular wall 37 into an inner annular chamber 38 and an outer annular chamber 39. As shown in FIG. 6, the outer annular chamber 39 has slots 40 around the outer periphery of the bulkhead wall 36, through which the outer annular chamber 39 communicates with the gap between the flow guide 34 and the outer jacket wall4l of the nozzle head 30. Cooling water is fed through a feed pipe 42 installed between the walls of the nozzle neck 33, the water flowing rapidly over the inner surface of the outer jacket wall 41 of the nozzle head 30 and around by the nozzle mouth and back over the surface of the inner jacket wall 43 of the noule head 30, that is to say between the flow guide 34 and the inner jacket wall 43. The water leaves the nozzle head 30 through slots 44 cut around the inner edge of the bulkhead wall 36. The water leaving the nozzle head flows through the inner annular chamber 38 and out through openings 45, evenly distributed around the channel plate 35, into the annular chamber between the walls of the nozzle neck 33 and out through an effluent duct 46, with cooling of the water.

As in the examples of tuyeres represented in FIGS. 1 to 3, the special method used for cooling the nozzle head 30 consists in that the channel cross section for the cooling water decreases where the water enters between the outer jacket wall 41 and the flow guide 34, this being where the tuyere is subjected to the greatest heat load, after which the channel cross section increases. Consequently the cooling water flows at a higher linear velocity over the hottest part of the jacket wall surface. Any vapor bubbles which form on the jacket wall surface are rapidly torn off again, ensuring intensive contact between the water and the wall surface.

The nozzle head 30 is detachable from the nozzle base 31, these two parts each being of welded construction. As shown in FIGS. 5 and 7 they are held together detachably by tie rods which pass through drillings 47 evenly distributed around the barrel 32. If the nozzle head 30 becomes damaged or worn out it can easily be replaced by a new one. Assembly is facilitates by a centering ring 49 projecting from the nozzle neck 33. A sealing ring 50 ensures a good seal between the nozzle neck 33 and the channel plate 35.

FIGS. 8 to 10 illustrate a simplified method for manufacturing the tuyeres according to the invention. The flow guide can for example be made of soft copper. The method allows the flow guide to be assembled in the nozzle head even if the latter has a complex cross section. In FIGS. 8 to 10 the nozzle head 61 has internal ribs 62 whose height decreases towards the nozzle mouth, leaving an internal space which increased in width towards the nozzle mouth, for accommodating the flow guide. The flow channel available for the cooling fluid decreases in cross sectional area towards the nozzle mouth. At the base of the nozzle head there is an inner ring 63 and an outer ring 64, leaving between them an annular gap which is conical in cross section. During assembly the flow guide 60 is introduced in the form of an annular bag through the conical annular gap, as shown to the left of the line Z Z in FIGS. 8 to 10, so that the bag comes to rest in the space between the ribs 62.

Into the mouth of the flow guide annular bag there is then introduced a ring 65 which is conical in cross section, the ring 65 squeezing the edges of the flo'w guide bag against the conical surfaces of the inner ring 63 and outer ring 64. The ring 65 has one or more drillings 66 through which the annular flow guide bag 60 can be inflated under pressure by the introduction of a hydraulic fluid 67, inflation being continued until the annular flow guide bag has come to rest with its outer surface everywhere in contact with the edgesof the ribs 62, as shown to the right of the line Z Z. A hydraulic fluid can be used for the inflation, or a gas, and after the inflation has been completed the fluid can be exhausted from the flow guide 60, which retains its shape, assuming that the wall, for example of copper is thick enough. However in the present example the pressure fluid 67 is a hardening synthetic plastic or a concrete or the like, which hardens in due course in the interior of the flow guide 60, if necessary with the help of heat. A flow guide 60 made by this method has considerable mechanical rigidity. As soon as the pressure fluid 67 has hardened sufficiently, the ring 65 is removed. The projecting edges of the flow guide bag are cut away and a plug ring 68 is welded in place between the inner ring 63 and the outer ring 64. The plug ring 68 has an annular extension 69. When the tuyere is in operation cooling fluid flows over the inner surface of the outer jacket wall, .through openings 70 cut into the outer ring 64 and along through the channels between the ribs towards the nozzle mouth and then around and back over the surface of the inner jacket wall, the cooling fluid finally passing out of the nozzle head through openings 71 cut into the inner ring 63. 7

FIGS. 11 and 12 shown a further example in which in contrast to the example shown in FIGS. 8 to 10, there are ribs 72 of constant height. At the base of the nozzle head there is a ring 73, instead of the inner and outer rings 63, 64, the ring 73 being welded before assembly in the mouth of a deep drawn copper annular flow guide bag 74. The pressure fluid is introduced into the flow guide 74 through drillings 75 in the ring 73. After the flow guide has been inflated the drillings 75 are plugged by plugs 76.

We claim:

1. A blast furnace tuyere with a nozzle which is arranged to project into the interior of a blast furnace, the nozzle being in the form of a double walled tubular jacket with a flow guide between the inner and outer walls for guiding cooling fluid to flow along the inner surfaces of the jacket walls around the guide, the flow guide occupying substantially the whole of the space between the inner and outer jacket walls adjacent to the nozzle mouth, leaving only a narrow gap through which the cooling fluid can flow, and the gap having a width of less than mm between the flow guide and the inner surface of the outer jacket wall.

A tuyere according to claim 1, in which the gap has a channel cross section which is constant along the flow path.

3. A tuyere according to claim 1, in which the gap has a circular flow path curvature where it changes direction.

4. A tuyere according to claim 1, in which the wall of the flow guide is thicker adjacent to the nozzle mouth than it is remote from the nozzle mouth.

5. A tuyere according to claim 1, in which, between the flow guide and the walls of the jacket adjacent the nozzle mouth there are longitudinal spacer ribs.

6. A tuyere according to claim 5, in that the ribs are a part of the jacket wall of the double walled jacket.

7. A tuyere according to claim 1, in which the gap contains several equally spaced ribs extending longitudinally, with respect to the longitudinal middle axis of the noule.

8. A tuyere according to claim 7, in which the gap is subdivided into separate channels by ribs, the width of I each rib and channel being less than twice the gap width.

9. A tuyere according to claim 1, in which several inlet openings for admitting a cooling fluid to the gap are equally spaced in a circle around the nozzle, the cooling fluid adapted to leave the gap through several outlet openings equally spaced on a circle around the nozzle.

10. A tuyere according to claim 9, in which the inlet openings are adapted to be fed with cooling fluid through a common annular chamber connected to a feed pipe, the outlet openings adapted to discharge cooling fluid to a common annular chamber connected to an effluent pipe.

11. A tuyere according to claim 1, in which the double walled jacket has a wall which is constant in thickness in the region of the gap.

12. A tuyere according to claim 11, in which the wall thickness of the double walled jacket is considerably less than the radius of curvature of the gap as seen in longitudinal section.

13. A tuyere according to claim 1, in which the nozzle consists of a neck part and a replaceable head part.

14. A tuyere according to claim 13, in which means are provided for cooling of the head part independent of the cooling of the neck part.

15. A tuyere according to claim 13, in which the base of the nozzle head where the nozzle head is attached to the nozzle neck has a double bottom subdivided into an outer annular chamber and an inner annular chamber, the outer annular chamber having inlet openings for the cooling fluid distributed equally around its outer periphery, for directing a stream of cooling fluid over the surface of the outer jacket wall of the nozzle head, the inner annular chamber having effluent openings for the cooling medium, equally spaced around its inner periphery, for receiving the cooling fluid which has been flowing over the surface of the inner jacket wall of the nozzle head.

16. A tuyere according to claim 1, in which the flow guide has a U-shaped longitudinal section in the head part.

17. A tuyere according to claim 1, in which the flow guide is a hollow body made of a flexible one of a highly elastic and highly plastic material of construction, the flow guide being arranged so that it can be inflated under pressure by the introduction of a pressure fluid.

18. A tuyere according to claim 17, in which the flow guide is made of one of rubber, a rubber like material a glass fiber reinforced plastic, and copper.

and one of a liquid and pasty hardenable substance contained within said flow guide for inflating it into the required shape.

21. A tuyere according to claim 20, in which the hardenable substance is one of a hardening plastic and a concrete.

l l k 

1. A blast furnace tuyere with a nozzle which is arranged to project into the interior of a blast furnace, the nozzle being in the form of a double walled tubular jacket with a flow guide between the inner and outer walls for guiding cooling fluid to flow along the inner surfaces of the jacket walls around the guide, the flow guide occupying substantially the whole of the space between the inner and outer jacket walls adjacent to the nozzle mouth, leaving only a narrow gap through which the cooling fluid can flow, and the gap having a width of less than 5 mm between the flow guide and the inner surface of the outer jacket wall.
 2. A tuyere according to claim 1, in which the gap has a channel cross section which is constant along the flow path.
 3. A tuyere according to claim 1, in which the gap has a circular flow path curvature where it changes direction.
 4. A tuyere according to claim 1, in which the wall Of the flow guide is thicker adjacent to the nozzle mouth than it is remote from the nozzle mouth.
 5. A tuyere according to claim 1, in which, between the flow guide and the walls of the jacket adjacent the nozzle mouth there are longitudinal spacer ribs.
 6. A tuyere according to claim 5, in that the ribs are a part of the jacket wall of the double walled jacket.
 7. A tuyere according to claim 1, in which the gap contains several equally spaced ribs extending longitudinally, with respect to the longitudinal middle axis of the nozzle.
 8. A tuyere according to claim 7, in which the gap is subdivided into separate channels by ribs, the width of each rib and channel being less than twice the gap width.
 9. A tuyere according to claim 1, in which several inlet openings for admitting a cooling fluid to the gap are equally spaced in a circle around the nozzle, the cooling fluid adapted to leave the gap through several outlet openings equally spaced on a circle around the nozzle.
 10. A tuyere according to claim 9, in which the inlet openings are adapted to be fed with cooling fluid through a common annular chamber connected to a feed pipe, the outlet openings adapted to discharge cooling fluid to a common annular chamber connected to an effluent pipe.
 11. A tuyere according to claim 1, in which the double walled jacket has a wall which is constant in thickness in the region of the gap.
 12. A tuyere according to claim 11, in which the wall thickness of the double walled jacket is considerably less than the radius of curvature of the gap as seen in longitudinal section.
 13. A tuyere according to claim 1, in which the nozzle consists of a neck part and a replaceable head part.
 14. A tuyere according to claim 13, in which means are provided for cooling of the head part independent of the cooling of the neck part.
 15. A tuyere according to claim 13, in which the base of the nozzle head where the nozzle head is attached to the nozzle neck has a double bottom subdivided into an outer annular chamber and an inner annular chamber, the outer annular chamber having inlet openings for the cooling fluid distributed equally around its outer periphery, for directing a stream of cooling fluid over the surface of the outer jacket wall of the nozzle head, the inner annular chamber having effluent openings for the cooling medium, equally spaced around its inner periphery, for receiving the cooling fluid which has been flowing over the surface of the inner jacket wall of the nozzle head.
 16. A tuyere according to claim 1, in which the flow guide has a U-shaped longitudinal section in the head part.
 17. A tuyere according to claim 1, in which the flow guide is a hollow body made of a flexible one of a highly elastic and highly plastic material of construction, the flow guide being arranged so that it can be inflated under pressure by the introduction of a pressure fluid.
 18. A tuyere according to claim 17, in which the flow guide is made of one of rubber, a rubber like material a glass fiber reinforced plastic, and copper.
 19. A tuyere according to claim 17, wherein the flow guide is formed of a comparatively stiff material such as copper, and a pressurized fluid medium contained within said flow guide for inflating it into the required shape.
 20. A tuyere according to claim 17, wherein the flow guide is formed of a flexible material such as rubber, and one of a liquid and pasty hardenable substance contained within said flow guide for inflating it into the required shape.
 21. A tuyere according to claim 20, in which the hardenable substance is one of a hardening plastic and a concrete. 